The Republican prosecutor became a symbol for his party’s political overreach in 2010, when he beat the establishment pick in a U.S. Senate primary, only to lose to Democratic Sen. Michael Bennet.

During the race, Tea Party favorite Buck was pounded for statements that angered some gays and women. Bennet’s surprise victory became a 2012 template for Democrats, including President Barack Obama, who went after their challengers’ statements on reproductive health and women’s rights.

Now Buck is back, having survived a bout with cancer, and is the front-runner in his party’s June primary to challenge Democratic Sen. Mark Udall. The race will test whether Republicans can avoid the mistakes that kept the Senate out of their hands in the last two elections. This time, the GOP needs a net gain of six seats to take charge.

“I fail to see how somebody who lost the winnable election in 2010 is the face of the future for this party,” state GOP Chairman Dick Wadhams said. “The same issues are going to come back.”

At a recent meeting of the Teller Tea Party Patriots, Buck seemed aware of the bigger picture when he answered an audience question about which federal agencies he would close.

“We have to talk responsibly,” Buck told the crowd inside a Denny’s. “The minute a Republican candidate says we need to do away with the Department of Education, the Democrats are running commercials saying Republicans don’t like school lunches. … I can’t tell you honestly that we can walk in and fire 8,000 employees.”

The shadow of 2010 hangs over Buck and the state party.

For much of the country, that was a banner year for Republicans. They rolled up more House seats than in any election in seven decades, netted six governorships and won at least 675 state legislative seats.

Colorado was a different story.

Buck lost what analysts considered a winnable Senate seat. A tea party favorite in the governor’s race split the GOP, leading firebrand Tom Tancredo, a former congressman, to run as a libertarian, and paving the way for Democrats to retain the seat.

Tancredo is now the front-runner in a crowded Republican primary field to challenge Democratic Gov. John Hickenlooper.

Wadhams prefers former state House Majority Leader Amy Stephens, but her voting with Democrats to create Colorado’s health exchange has angered some party activists. Two state senators, Randy Baumgardner and Owen Hill, also are running.

Buck and his backers argue that the 54-year-old district attorney won’t have to go through such a bruising primary, knows what Democrats will throw at him and is ready to shift the debate back to economic issues that they believe help the GOP.

“People will get to know me this time and they will understand that material in perspective,” Buck said in an interview.

Last time, Democrats savaged Buck for his dig at his primary opponent, former Lt. Gov. Jane Norton, for wearing “high heels,” for his support for an initiative to give a fertilized egg legal rights and for his comparison of homosexuality to alcoholism.

Walt Klein, a veteran strategist who worked on Buck’s prior Senate bid and is helping him again, says Buck “has benefited from the trials and tribulations of the 2010 campaign. He is even more focused and energized.”

Democrats who have campaigned against Buck say he is a more adept politician than the gaffe-prone stereotype that lingered after 2010.

But Guy Cecil, who ran Bennet’s campaign and is now head of the Democratic Senatorial Campaign Committee, says that what matters most are the policies that Buck and his opponents must embrace to win the primary.

“The question is what happens when you draw a contrast between an independent Colorado moderate like Mark Udall and a candidate who operates on the extremes,” Cecil said. “You can certainly look at the rest of the Republican field in Colorado and they share the same positions” as Buck.

Buck said in the interview that he didn’t start thinking about a second try at the Senate until well after he lost to Bennet by 29,000 votes out of more than 1.7 million cast. Before he could figure out what he wanted to do, he was diagnosed with stage 4 lymphoma last March.

“I had 22 tumors in my neck,” he told the crowd at Denny’s. “I had 12 tumors in my arm. I had cancer in my spleen.” Buck said the doctor said he’d be dead in three months without chemotherapy.

The cancer vanished after three chemotherapy sessions. Buck said he decided his heart was in trying again to go to Washington and shrink the federal government.

In his appearance in Woodland Park, a bedroom community at the base of Pikes Peak and a short commute to Colorado Springs, Buck’s political skills were apparent. Dressed in a gray sweater, jeans and cowboy boots, he kept the crowd happy with denunciations of Obama and Udall. He cited the cancer to show his motivation to win and also to bash Obama’s health care package.

But he refused to be baited into incendiary statements.

One questioner asked him to grade a range of GOP senators, from tea party favorite Ted Cruz of Texas to Arizona’s John McCain, the mention of whose name evoked scowls and grumbling.

Buck noted he was going to have to work with all senators and that he would give none a failing grade.

Someone else in the audience wanted to have U.S. Supreme Court Justice Elena Kagan impeached, to invalidate last year’s ruling upholding the constitutionality of Obama’s health care law. Buck dismissed that idea, say the high court’s decision was the law of the land.

To hammer home one point, he told the story of a local official he had met during his latest swing through all of Colorado’s 64 counties. Then he paused, as if struck by an idea.

“You know,” he said, “I love running for office. I may do it the rest of my life – after I win.”